Thermal spray for solar concentrator fabrication

ABSTRACT

A system may include an optical element, a thermal-sprayed material disposed on the optical element, and a solar cell coupled to the optical element. Some aspects provide thermal spraying of a first material onto an optical element, and coupling of a solar cell to the optical element. Thermal spraying the first material may include spraying a molten metal powder onto the optical element.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 60/899,150, filed on Feb. 2, 2007 and entitled“Concentrated Photovoltaic Energy Designs”, the contents of which areincorporated herein by reference for all purposes.

BACKGROUND

1. Field

Some embodiments generally relate to the collection and concentration ofsolar radiation. More specifically, embodiments may relate to systems toefficiently fabricate solar radiation collectors.

2. Brief Description

A concentrating solar radiation collector may convert received solarradiation (i.e., sunlight) into a concentrated beam and direct theconcentrated beam onto a small photovoltaic cell. The cell, in turn,converts the photons of the received beam into electrical current.

U.S. Patent Application Publication No. 2006/0231133 describes severaltypes of concentrating solar collectors. As described therein, aconcentrating solar collector may include reflective material fordirecting received solar radiation, conductive material to carryelectrical current generated from the solar radiation, and/or insulativematerial to isolate various conductors from one another. Fabrication ofa solar radiation collector using one or more of these materials may beunsuitably complex and costly.

For example, conventional techniques for depositing these materials mayinclude evaporating or sputtering within an established vacuum. Thinfilm lithographic techniques are employed to create desired patterns andfeatures in the deposited materials. Such techniques require photoresistdeposition, masking, UV exposure, and subsequent etching for each layerof material. Thin film lithography may provide geometrically accuracybut entails significant expense.

SUMMARY

To address at least the foregoing, some aspects provide a method, meansand/or process steps to thermal spray a first material onto an opticalelement, and to couple a solar cell to the optical element. Thermalspraying the first material may include spraying a molten metal powderonto the optical element. Moreover, spraying the molten metal powderonto the optical element may include placing a stencil on the opticalelement and spraying a molten metal powder onto the stencil and theoptical element.

In some aspects, thermal spraying the first material includes powdercoating a polymer onto the optical element. According to still otheraspects, a reflective material is deposited on asubstantially-transparent core, an insulator is deposited on thereflective material, and thermal spraying the first material includesspraying a molten metal powder onto the insulator.

In other aspects, provided are an optical element, a thermal-sprayedmaterial disposed on the optical element, and a solar cell coupled tothe optical element. The thermal-sprayed material may comprise ahardened metal powder. In further aspects, the optical element maycomprise an aperture from which light may pass out of the opticalelement, an electrical contact of the solar cell is coupled to thehardened metal powder, and an optically-active area of the solar cell isaligned with the aperture.

The thermal-sprayed material may comprise a polymer. Additionally oralternatively, the optical element may comprise asubstantially-transparent core, a reflective material disposed on thesubstantially-transparent core, and an insulator disposed on thereflective material, wherein the thermal-sprayed material is disposed onthe insulator. Further to the foregoing aspect, the insulator mayinclude a powder-coated polymer.

The claims are not limited to the disclosed embodiments, however, asthose in the art can readily adapt the description herein to createother embodiments and applications.

BRIEF DESCRIPTION OF THE DRAWINGS

The construction and usage of embodiments will become readily apparentfrom consideration of the following specification as illustrated in theaccompanying drawings, in which like reference numerals designate likeparts.

FIG. 1 is a flow diagram of a method according to some embodiments.

FIG. 2A is a perspective view of a portion of an optical element andconductive material according to some embodiments.

FIG. 2B is a cross-sectional view of a portion of an optical element andconductive material according to some embodiments.

FIG. 3A is a perspective view of a portion of an optical element and asolar cell coupled thereto according to some embodiments.

FIG. 3B is a perspective view of a portion of an optical element and asolar cell coupled thereto according to some embodiments.

FIG. 4 is a flow diagram of a method according to some embodiments.

FIG. 5A is a perspective view of a transparent optical element accordingto some embodiments.

FIG. 5B is a cross-sectional view of a transparent optical elementaccording to some embodiments.

FIG. 6A is a perspective view of a transparent optical element withreflective material disposed thereon according to some embodiments.

FIG. 6B is a cross-sectional view of a transparent optical element withreflective material disposed thereon according to some embodiments.

FIG. 7A is a perspective view of an optical element with an electricalisolator disposed thereon according to some embodiments.

FIG. 7B is a cross-sectional view of an optical element with anelectrical isolator disposed thereon according to some embodiments.

FIG. 8A is a perspective view of an optical element with conductivematerial disposed thereon according to some embodiments.

FIG. 8B is a cross-sectional view of an optical element with conductivematerial disposed thereon according to some embodiments.

FIG. 9 is a cross-sectional view of an optical element and a solar cellaccording to some embodiments.

DETAILED DESCRIPTION

The following description is provided to enable any person in the art tomake and use the described embodiments and sets forth the best modecontemplated for carrying out some embodiments. Various modifications,however, will remain readily apparent to those in the art.

FIG. 1 is a flow diagram of process 100 according to some embodiments.Process 100 may be performed by any combination of machine, hardware,software and manual means.

Initially, at S110, a first material is thermal sprayed onto an opticalelement. The first material may comprise any material that is capable ofbeing thermally-sprayed. Thermal spraying the first material may includeheating a powder to a molten state and spraying the molten powder ontothe optical element. The molten powder then cools on the optical elementto produce a solid layer of material. In some embodiments, a stencil maybe applied to the optical element before spraying the molten powder ontothe optical element. The first material is therefore deposited in apattern defined by the stencil.

The thermal spraying may be performed using a known twin wire arcprocess in a case that the first material is a metal. Plasma spraytechniques may be employed at S110 if the first material is a metal or aceramic. Moreover, if the first material is a polymer (e.g., polyester,epoxy, polyurethane, etc.), the first material may be powder coated ontothe optical element at S110. Accordingly, the term thermal sprayingencompasses at least twin wire arcing, plasma spraying (e.g., hot, cold,assisted), and powder coating.

Thermal spraying the first material onto the optical element maycomprise spraying the first material onto other material(s) alreadydeposited on the optical element. According to some embodiments, theoptical element may be configured to manipulate and/or pass desiredwavelengths of light. The optical element may comprise any number ofdisparate materials and/or elements (e.g., lenses, reflective surfacesand optically-transparent portions).

FIG. 2A is a perspective view of apparatus 200 according to someembodiments, and FIG. 2B is a cross-sectional view of apparatus 200 asshown in FIG. 2A. Apparatus 200 includes optical element 220 andconductive material 210 sprayed thereon according to some embodiments ofS110. FIGS. 2A and 2B show only a portion of apparatus 200 in order toillustrate that apparatus 200 may exhibit any suitable shape or size.

Conductive material 210 may comprise any combination of one or morecurrently- or hereafter-known conductors, including but not limited tocopper, gold and nickel. A thickness of material 210 on optical element220 might not be as uniform as shown in FIG. 2B.

A solar cell is coupled to the optical element at S120. The coupling atS120 may comprise coupling the solar cell to other material(s) alreadydeposited on the optical element. For example, an electrical contact ofthe solar cell may be coupled to conductive material deposited on theoptical element. Such a coupling may form an electrical and a mechanicalinterconnection between the conductive material and the solar cell.Various flip-chip bonding techniques may be employed in some embodimentsto couple an electrical contact of the solar cell to conductive materialdeposited on the optical element.

FIG. 3A is a perspective view of apparatus 200 after S120 according tosome embodiments. FIG. 3B is a cross-sectional view corresponding toFIG. 3A. Solder bumps 305 of solar cell 300 are coupled to conductivematerial 210. Solder bumps 305 may also be respectively coupled tounshown terminals of solar cell 300.

Solar cell 300 may comprise a solar cell (e.g., a III-V cell, II-VIcell, etc.) for receiving photons from optical element 220 andgenerating electrical charge carriers in response thereto. In thisregard, some embodiments include an opening through dielectricconductive material 210 through which solar cell 300 may receive lightfrom optical element 220.

FIG. 4 is a flow diagram of process 400 according to some embodiments.Process 400 may be performed by any combination of machine, hardware,software and manual means.

Process 400 begins at S410, at which an optical element is obtained. Theoptical element may be composed of any suitable material or combinationof materials. The optical element may be created using any combinationof devices and systems that is or becomes known.

FIG. 5A is a perspective view of optical element 500 created at S410according to some embodiments, and FIG. 5B is a cross-sectional view ofelement 500. Optical element 500 may be molded from low-iron glass atS410 using known methods. Alternatively, separate pieces may be glued orotherwise coupled together to form element 500. Optical element 500 maycomprise an element of a solar concentrator according to someembodiments.

Element 500 includes convex surface 510, pedestal 520, and concavesurface 530. The purposes of each portion of element 500 duringoperation according to some embodiments will become evident from thedescription below.

A reflective material is deposited on the optical element at S420. Thereflective material may be intended to create one or more mirroredsurfaces. Any suitable reflective material may be used, taking intoaccount factors such as but not limited to the wavelengths of light tobe reflected, bonding of the reflective material to the optical element,and cost. In some embodiments, the reflective material may include amirror coating, a dielectric enhancement coating, and/or a protectivedielectric or polymer paint coating. The reflective material may bedeposited by sputtering or other physical vapor deposition, liquiddeposition, etc.

FIGS. 6A and 6B show perspective and cross-sectional views,respectively, of optical element 500 after some embodiments of S420.Reflective material 540 is deposited on convex surface 510 and concavesurface 530. Reflective material 540 may comprise sputtered silver oraluminum. The vertical and horizontal surfaces of pedestal 520 may bemasked at S420 such that reflective material 540 is not depositedthereon, or otherwise treated to remove any reflective material 540 thatis deposited thereon.

Next, at S430, a polymer is powder-coated onto the optical element. Thepolymer may comprise an electrical insulator, and the powder-coating mayproceed according to any method that is or becomes known. The polymermay act as a mechanical buffer layer between the reflective material andconductive material. This buffer layer can also be deposited by othermeans such as spraying, dipping or lamination. According to someembodiments, other suitable insulators such as any dielectrics,polyester, epoxy and polyurethane are powder-coated onto the opticalelement at S430.

Some embodiments of S430 are depicted in FIGS. 7A and 7B. Polymer 550 isdeposited on convex surface 510 or, more particularly, on reflectivematerial 540. S615 may be executed such that polymer 550 is notdeposited on the vertical and horizontal surfaces of pedestal 520.According to the illustrated embodiment, polymer 550 is not deposited onconcave surface 530 (i.e., on reflective material 540 deposited onconcave surface 530).

Returning to process 400, a stencil is placed on the optical element atS440 and a molten metal powder is sprayed on the stencil and the opticalelement at S450. The stencil may comprise a mechanical, hard or softtooling. The stencil may cover portions of the previously-depositedpolymer that are not to receive the molten metal powder. The moltenmetal powder may be composed of any combination of one or more metals(e.g., nickel, copper).

FIG. 8A is a perspective view and FIG. 8B is a cross-sectional view ofoptical element 500 after S450 according to some embodiments. Conductivematerial 560 covers pedestal 520 and portions of insulator 550.Conductive material 570 is also sprayed at S450 and also covers portionsof insulator 550. A stencil in the shape of the illustrated gap betweenconductive material 560 and conductive material 570 was placed at S440.The gap may facilitate electrical isolation between conductive material560 and conductive material 570.

Aperture 565 may comprise an exit window for light entering element 500.The stencil placed at S440 may also define aperture 565. Such a stencilmay comprise a mechanical, a liquid or a solid mask which is removed(i.e., peeled or dissolved) after S450.

Although conductive materials 560 and 570 appear to extend to a uniformheight above element 500, this height need not be uniform. Conductivematerials 560 and 570 may create a conductive path for electricalcurrent generated by a photovoltaic (solar) cell coupled to element 500.Conductive material 560 and conductive material 570 may also, asdescribed in U.S. Patent Application Publication No. 2006/0231133,electrically link solar cells of adjacent solar concentrators in a solarconcentrator array.

An electrical contact of a solar cell is coupled to the metal sprayedonto the optical element at S460. The electrical contact may comprise asolder bump, and any number of intermediate conductive elements such asvarious layers of bonding pads may be used to couple the electricalcontact to the exposed portion. Coupling the electrical contact to themetal may comprise any flip-chip bonding techniques that are or becomeknown. For example, the electrical contact may be placed on the metalusing a pick-and-place machine, and the optical element and solar cellmay be placed in a reflow oven to melt and subsequently cool theelectrical contact.

FIG. 9 shows solder bumps 910 of solar cell 900 coupled to conductivematerial 560. Window 920 of solar cell 900 covers an optically-activearea of solar cell 900. Accordingly, solder bumps 910 are coupled toconductive material 560 in some embodiments such that theoptically-active area is aligned with aperture 565.

Apparatus 500 of FIG. 9 may generally operate in accordance with thedescription of aforementioned U.S. Patent Application Publication No.2006/0231133. With reference to FIG. 9, solar rays enter surface 598 andare reflected by reflective material 540 disposed on convex surface 510.The rays are reflected toward reflective material 540 on concave surface530, and are thereafter reflected toward aperture 565. The reflectedrays pass through aperture 565 and are received by window 920 of solarcell 900. Those skilled in the art of optics will recognize thatcombinations of one or more other surface shapes may be utilized toconcentrate solar rays onto a solar cell.

Solar cell 900 receives a substantial portion of the photon energyreceived at surface 598 and generates electrical current in response tothe received photon energy. The electrical current may be passed toexternal circuitry (and/or to similar serially-connected apparatuses)through conductive material 560 and conductive material 570. In thisregard, solar cell 900 may also comprise an electrical contactelectrically coupled to conductive material 570. Such a contact wouldexhibit a polarity opposite to the polarity of the contacts to whichsolder bumps 910 are coupled.

The several embodiments described herein are solely for the purpose ofillustration. Embodiments may include any currently or hereafter-knownversions of the elements described herein. Therefore, persons in the artwill recognize from this description that other embodiments may bepracticed with various modifications and alterations.

1. A method comprising: thermal spraying a first material onto anoptical element; and coupling a solar cell to the optical element.
 2. Amethod according to claim 1, wherein thermal spraying the first materialcomprises spraying a molten metal powder onto the optical element.
 3. Amethod according to claim 2, wherein spraying the molten metal powderonto the optical element comprises: placing a stencil on the opticalelement; and spraying a molten metal powder onto the stencil and theoptical element.
 4. A method according to claim 3, further comprising:removing the stencil to expose an aperture from which light may pass outof the optical element, wherein coupling the solar cell to the opticalelement comprises: coupling an electrical contact of the solar cell tothe first material to align an optically-active area of the solar cellwith the aperture.
 5. A method according to claim 3, wherein the stencilcomprises a mechanical, hard or soft tooling.
 6. A method according toclaim 1, wherein thermal spraying the first material comprises powdercoating a polymer onto the optical element.
 7. A method according toclaim 1, further comprising: depositing a reflective material on asubstantially-transparent core; and depositing an insulator on thereflective material; wherein thermal spraying the first materialcomprises spraying a molten metal powder onto the insulator.
 8. A methodaccording to claim 7, wherein depositing the insulator comprises powdercoating a polymer onto the reflective material.
 9. A method according toclaim 7, wherein depositing the reflective material comprises physicalvapor deposition of the reflective material onto thesubstantially-transparent core.
 10. A method according to claim 7,wherein thermal spraying the first material comprises: placing a stencilon the insulator; and spraying a molten metal powder onto the stenciland the insulator.
 11. A method according to claim 1, wherein thermalspraying the first material onto the optical element comprises: placinga stencil on the optical element; and spraying the first material ontothe stencil and the optical element.
 12. A method according to claim 1,wherein coupling the solar cell to the optical element comprisescoupling an electrical contact of the solar cell to the first materialto align an optically-active area of the solar cell with an aperturefrom which light may pass out of the optical element.
 13. An apparatuscomprising: an optical element; a thermal-sprayed material disposed onthe optical element; and a solar cell coupled to the optical element.14. An apparatus according to claim 13, wherein the thermal-sprayedmaterial comprises a hardened metal powder.
 15. An apparatus accordingto claim 14, wherein: the optical element comprises an aperture fromwhich light may pass out of the optical element, an electrical contactof the solar cell is coupled to the hardened metal powder, and anoptically-active area of the solar cell is aligned with the aperture.16. An apparatus according to claim 13, wherein the thermal-sprayedmaterial comprises a polymer.
 17. An apparatus according to claim 13,wherein the optical element comprises: a substantially-transparent core;a reflective material disposed on the substantially-transparent core;and an insulator disposed on the reflective material, wherein thethermal-sprayed material is disposed on the insulator.
 18. An apparatusaccording to claim 17, wherein the insulator comprises a powder-coatedpolymer.
 19. An apparatus according to claim 13, wherein: the opticalelement comprises an aperture from which light may pass out of theoptical element, an electrical contact of the solar cell is coupled tothe thermal-sprayed material, and an optically-active area of the solarcell is aligned with the aperture.